Syringes including frangible barrels of the replaceable type are used extensively in the livestock industry for the purpose of vaccinating livestock. The frangible syringe barrels are subject to frequent breakage during a day's use and breakage of the barrel not only requires its replacement at considerable cost but also interrupts the vaccinating operation with the resultant loss in time of many persons involved in a large scale vaccinating operation. In addition, breakage of the frangible barrel can also result in damage to the piston defining O-ring of the syringe as well as various sealing O-rings thereof and necessitate their replacement at additional cost.
Various forms of syringes suitable for large scale vaccinating operations have been heretofore designed, but those provided with frangible syringe barrels do not include sufficient means for protecting the frangible barrels against breakage.
Examples of various forms of syringes including some of the structural features of the basic syringe structure of the instant invention are disclosed in U.S. Pat. Nos. 3,160,156 and 3,797,489.